1. Field of the Invention
The present invention relates to a manufacturing method of a ceramic green sheet. Moreover, the present invention relates to a manufacturing method of a multilayer ceramic electronic component containing a manufacturing process of a laminated body of the above-described ceramic green sheet, and to a carrier sheet for ceramic green sheets used for the manufacturing method of the ceramic green sheet concerned. Furthermore, the present invention relates to a multilayer ceramic electronic component obtained by the manufacturing method of the above-described multilayer ceramic electronic component.
2. Description of the Prior Art
A multilayer ceramic electronic component as a multilayer ceramic capacitor or an inductor, they are manufactured in a method in which predetermined number of sheets of ceramic green sheets with internal electrodes prepared thereon are laminated, since electrodes are required inside. And baked with heat and furthermore external electrodes are applied to an edge part. Especially, in a multilayer ceramic capacitor, etc., a number of laminating of the above-described ceramic green sheets is required to be increased within a limited thickness, since a miniaturization and high performance are highly required. Therefore, in order to increase a number of lamination a thickness of the ceramic green sheet is made thinner.
As a laminating method of a ceramic green sheet, a method may be mentioned in which after electrode patterns used as internal electrodes are formed on a ceramic green sheet a predetermined number of sheets of the ceramic green sheet are laminated. However, since this method has a process in which electrodes are printed on a ceramic green sheet, a convex part is generated by thickness of electrodes formed and then the thickness is added up as a number of laminated layer is increased. As a result, possible shift between ceramic green sheets, etc. may be caused, and lamination with expected accuracy cannot be attained. Moreover, the ceramic green sheet, after laminated, is pressed under a high pressure in order to expect better integration. In this case, a difference between pressure in a portion in which electrodes exist and a portion in which electrodes do not exist may be generated to cause a high possibility of a separation, etc., of a decrease in yield and a possibility of a defect.
As a method to solve problems of the above-described laminating method of ceramic green sheet, a method is proposed in which operation is repeatedly performed that after formation of an electrode pattern used as internal electrodes on a carrier sheet, a ceramic green sheet is formed with a ceramic slurry, and subsequently obtained ceramic green sheet is laminated onto other ceramic green sheets (JP, 6-61090, A, etc.) . In a ceramic green sheet obtained by the method, since the electrodes are embedded inside, the green sheet does not have convex parts caused by electrodes and an ideal lamination and thin film formation may be realized. Moreover, the pressure non-uniformity generated in the press processing after lamination does not occur, and better integration is realized with better yield of a product and further a higher performance by highly multiple lamination may be expected.
In the laminating method of the above-described ceramic green sheet, since a ceramic green sheet is formed on a carrier sheet that is finally to be separated, the carrier sheet is required to have separable property that it may be separated easily from the obtained ceramic green sheet. Furthermore, in a carrier sheet, patterning accuracy must be secured so that a shift between electrodes may not occur when the electrode pattern used as internal electrodes are formed. However, any examples satisfying the above-described demand is not known in conventional carrier sheet for ceramic green sheets.
An object of the present invention is to provide a method for manufacturing a ceramic green sheet in which electrodes may be formed with good patterning accuracy and a carrier sheet may easily separated after formation of the ceramic green sheet. Namely, an object of the present invention is to provide a method for efficiently manufacturing a ceramic green sheet with high accuracy having internal electrodes embedded therein.
Moreover an object of the present invention is to provide a method of manufacturing a multilayer ceramic electronic component by laminating the ceramic green sheet manufactured by the manufacturing method of the above-described ceramic green sheet, and further to provide a multilayer ceramic electronic component manufactured by the manufacturing method concerned.
Moreover, an object of the present invention is to provide a carrier sheet for ceramic green sheets, used for a manufacturing method of the above-described ceramic green sheet and a manufacturing method of a multilayer ceramic electronic component.
As a result of wholehearted and repeated examination to solve the above-described subject, the present inventors found out that the above-described objection is attained by a method using the following carrier sheets for ceramic green sheets, and thus the present invention was completed.
The present invention relates to a manufacturing method of a ceramic green sheet comprising steps of;
forming a predetermined electrode pattern on an adhesive layer separable by being heated or an adhesive layer separable by being cured with UV of a carrier sheet, wherein the carrier sheet comprising the separable adhesive layer on one side of a base film,
and forming a ceramic green sheet with a ceramic slurry on the separable adhesive layer with the electrode pattern formed thereon.
In the above-described manufacturing method of a ceramic green sheet of the present invention, a carrier sheet is used having an adhesive layer separable by being heated or an adhesive layer separable by being cured with UV instead of a film in which treatment for separation is applied by silicone treatment, etc., in order to develop a separable property in a carrier sheet.
An adhesive layer separable by being heated of the above-described carrier sheet loses adhesion easily when heated, and develops a separable property. Thus, a ceramic green sheet and a carrier sheet are easily separable by being heated after the ceramic green sheet is formed or laminated. Moreover, an adhesive layer separable by being heated shows a certain level of adhesion, and thus wettability when applied is secured in a forming process of a ceramic green sheet in which the ceramic slurry is applied. Therefore, a green sheet in which an electrode pattern is formed with excellent patterning accuracy on a carrier sheet side may be manufactured, without deteriorating patterning accuracy of a location of a formed internal electrode pattern.
In the manufacturing method of the above-described ceramic green sheet, a method is preferable in which the adhesive layer separable by being heated of a carrier sheet foams when heated, and makes a separation with ease. When an adhesive layer separable by being heated foams with heat, the adhesion area between the carrier sheet and the ceramic green sheet is decreased, and then an adhesive strength is weakened, and as a result the carrier sheet and the ceramic green sheet maybe separated easily. As an adhesive layer separable by being heated in such a carrier sheet, for example, a type with a constitution in which thermal expandable fine-particles are contained in the adhesive layer may be suitably used.
Moreover, in the manufacturing method of the above-described ceramic green sheet, it is preferable that wherein a dynamic modulus of elastic of an adhesive forming the adhesive layer separable by being heated is in a range of 5xc3x97103 to 1xc3x97106 Pa at a temperature of 23 degrees C. to 150 degrees.
In order that internal electrodes may be formed with excellent patterning accuracy and moreover that it may be easily separated when heated after manufacture of a ceramic green sheet, an adhesive that forms the adhesive layer separable by being heated on the carrier sheet may preferably be a high elastic polymer having a dynamic modulus of elastic in the above-described range. When the above-described dynamic modulus of elastic is low, the thermal expandable fine-particles contained in an adhesive layer separable by being heated is flowing, and then the fine-particles cannot develop enough effect reducing adhesion area by foaming with heat to cause a tendency of difficulty in separation of the carrier sheet. Therefore, the above-described dynamic modulus of elastic is no less than 5xc3x97103 Pa, and preferably no less than 5xc3x97104 Pa. On the other hand, if the above-described dynamic modulus of elastic becomes high, there is a tendency for a fault of an electrode shift and for a patterning accuracy to be spoiled when ceramic slurry is applied after an electrodes are printed with electric conductive paste, etc. Moreover, when an electrode is formed by transferring method (removed and printed) of a metallic foil, if the above-described dynamic modulus of elastic is high, a poor transfer may occur, and as a result there is a tendency for an accurate electrode pattern no longer to be obtained. For this reason, the above-described dynamic modulus of elastic is preferably controlled no more than 1xc3x97106 Pa, and more preferably no more than 8xc3x97105 Pa. In addition, the above-described dynamic modulus of elastic is a value measured using dynamic viscoelasticity measurement equipment a Rheometrics ARES spectrometer (frequency of 1 Hz, 2 mm of sample thickness, 100 g of pressure loads).
Moreover, as an adhesive layer separable by being heated on the above-described carrier sheet, for example, a type containing a side chain crystalline resin in the adhesive layer is suitably used. A side chain crystalline resin represents a resin in which a side chain crystallizes at no less than a certain temperature.
In the manufacturing method of the above-described ceramic green sheet, an adhesive strength to stainless steel of the adhesive layer separable by being heated is preferably more than 0.1 N/20 mm at ordinary temperature (23 degrees C.), and is no more than 0.1 N/20 mm when heated. The adhesive layer separable enables adhesion to decrease when heated and also makes a separation easier. In order that a shift of printing may not occur when an electrode is formed on a carrier sheet, and that a poor transfer may not be obtained when electrodes are formed by transferring method (removed and printed) of a metallic foil, but in order to obtain an electrode pattern with excellent accuracy, the adhesive strength of an adhesive layer separable by being heated is preferably more than 0.1 N/20 mm at ordinary temperature (23 degrees C.), and preferably no less than 0.2 N/20 mm. Moreover, the adhesive strength of the adhesive layer when heated is preferably controlled to no more than 0.1 N/20 mm, and more preferably no more than 0.05 N/20 mm. Adhesive strength represents an adhesive strength to a stainless steel board (SUS 304BA) here according to a usual adhesive strength measuring method (JIS C 2107) (measuring conditions: a width of 20 mm, 2 kg of loads).
Now, the above-described adhesive layer separable by being cured with UV has a character to be cured with UV irradiation to form three-dimensional cross-links. This adhesive layer separable by being cured with UV loses adhesion easily with UV irradiation, and develops a separable property. When UV irradiation is applied after a ceramic green sheet is formed or laminated, the ceramic green sheet and the carrier sheet may be easily separated from each other. Moreover, an adhesive layer separable by being cured with UV shows a certain level of adhesion, and, thereby, the wettability in case of application is secured during a forming process of the ceramic green sheet in which a ceramic slurry is applied. Therefore, a green sheet in which an electrode pattern is formed in the carrier sheet side with an excellent patterning accuracy may be manufactured, without lowering the position accuracy of the internal electrode pattern to be formed.
In the manufacturing method of the above-described ceramic green sheet, an adhesive strength at ordinary temperature (23 degrees C.) to stainless steel of an adhesive layer separable by being cured with UV is preferably more than 0.1 N/20 mm before UV irradiation and no more than 0.1 N/20 mm after UV irradiation. An adhesive layer separable by being cured with UV represents an adhesive layer that loses adhesion with UV irradiation to enable an easy separation. In order that a shift of printing may not occur when an electrode is formed on a carrier sheet, and that a poor transfer may not be obtained when electrodes are formed by transferring method (removed and printed) of a metallic foil, but in order to obtain an electrode pattern with excellent accuracy, the adhesive strength of adhesive layer separable by being cured with UV is preferably more than 0.1 N/20 mm at ordinary temperature (23 degrees C.), and more preferably no less than 0.15 N/20 mm, and further preferably no less than 0.2 N/20 mm before UV irradiation. Moreover, the adhesive strength of the adhesive layer after UV irradiation is controlled to no more than 0.1 N/20 mm, and preferably no more than 0.05N/20 mm. Adhesive strength represents an adhesive strength to a stainless steel board (SUS 304BA) here according to a usual adhesive strength measuring method (JIS C 2107) (measuring conditions: a width of 20 mm, 2 kg of loads).
Moreover, the present invention relates to a manufacturing method of a multilayer ceramic electronic component comprising steps of;
laminating a ceramic green sheet onto other ceramic green sheets, after manufacturing the ceramic green sheet by the above-described method,
and separating the carrier sheet from the ceramic green sheet by being heated or irradiated with UV.
The ceramic green sheet manufactured by the above-described manufacturing method may easily be released and separated from the carrier sheet by heating or UV irradiation, and moreover a high accuracy and precision are attained in a laminated body of the ceramic green sheet, without any shift of electrodes. Especially, an effect excellent is attained, in manufacturing of a highly multilayered ceramic capacitor in which a number of laminating exceeds 100 layers.
Moreover, the present invention relates to a carrier sheet for a ceramic green sheets used for the manufacturing method of the above-described ceramic green sheet or for the manufacturing method of the above-described multilayer ceramic electronic component, comprising an adhesive layer separable by being heated or an adhesive layer separable by being cured with ultraviolet on one side of a base film.
Using such a carrier sheet for ceramic green sheets, internal electrodes with a good patterning accuracy maybe formed, and moreover the carrier sheet may easily be separated from the ceramic green sheet, and thus a ceramic green sheet, a laminated body thereof, and further a multilayer ceramic electronic component may efficiently be manufactured.
Furthermore, the present invention relates to a multilayer ceramic electronic component obtained by the manufacturing method of the above-described multilayer ceramic electronic component.